Low nitrogen supply decreases water‐use efficiency of oriental tobacco

Most studies indicating positive effects of nitrogen (N) supply on biomass water‐use efficiency (WUE) used two contrasting levels of N supply and monitored some of the relevant traits being associated with WUE. In order to investigate N effects on WUE over a wider range of N‐supply levels, oriental tobacco was cultivated in pots under six (Exp. 1) and four (Exp. 2) N levels until flowering stage. Water‐use efficiency, intrinsic water‐use efficiency (A/g), carbon isotope discrimination (CID), average daily canopy transpiration rate (E_C; from 12 to 7 d before harvest), and biomass‐partitioning parameters were determined. Water‐use efficiency increased from the lowest to the highest N level and was positively correlated with biomass. Intrinsic water‐use efficiency was positively correlated with leaf N and chlorophyll concentration. Whole‐plant CID was significantly less negative under high compared to low N supply. Biomass‐partitioning parameters were only slightly affected by N supply except for leaf‐area ratio, which significantly increased with N supply. The low planting density of Exp. 2 resulted in an increase of WUE and substantially less negative whole‐plant CID compared to Exp. 1. In both experiments, E_C was lower under high compared to low N supply and was negatively correlated with WUE. It is concluded that plants under high N supply realized a higher WUE via increases of A/g and a reduction of E_C.     

Effects of nitrogen supply on water‐use efficiency of higher plants

The worldwide increase of food demand and reduced sweet‐water availability in some important food‐producing regions raised interest in more efficient water use, which has become one of the central research topics in agriculture. Improved irrigation management and reduced bare‐soil evaporation have highest priority to increase agronomic water‐use efficiency (WUE). Compared to these technical (irrigation) and basic (crop production) management options, effects of nutrient management on WUE were less frequently considered. Twenty‐nine publications on nitrogen (N) effects on biomass WUE of container‐grown plants are considered in this review. Most of them indicate positive N effects on WUE, and relevance of N effects on intrinsic WUE and unproductive water and carbon loss is discussed. A plot of 90 published data of percent decreases of WUE and dry mass under variable N supply is presented. Extrapolation of biomass WUE from leaf measurements of intrinsic WUE is critically reviewed. The positive correlation between WUE and dry‐mass formation suggests that physiological rather than stomatal effects are more important in order to explain positive N effects on WUE.     

Nutrient use efficiency (NUE) for sustainable wheat production: a review

Abstract

In the last five decades, nutrient applications to farmlands have significantly improved crop yield and public awareness about nutrient use efficiency (NUE). The crop production system is nutrient-dependent in unfertile lands. The ideal management applications are used to enhance the NUE i.e. application of nutrients at right place and time with right rate. However, there must be a balance among the crop productivity and NUE. The maximum NUE is always observed where nutrient supply is lowest. The use of vital plant nutrients is significant for agricultural sustainability. However, the application of essential nutrient is under the influence of plant, climate, and economic conditions of farmers. In general agro-climatic conditions, the crop has fertilizer or NUE below 50%. The lower NUE is directly proportional to excess stability of nutrients, which may cause environmental pollution. Enhancement in NUE is crucial in agro-economical point of view. Improvement in plant nutrition e.g. P, N, and K, is the need of the hour to achieve food and fiber. In this review, we focused on discussing the significance of NUE and how NUE can be enhanced. There should be a balance among optimum NUE and excellent crop production.     

Mathematical model for the analysis of irrigation water and fertilizer management for spring wheat in the semiarid area of West Liaoning,China

Soybean plants (Glycine max L. cv. Akisengoku) were grown in water culture in a greenhouse. At the pod-setting and pod-filling stages, plants were subjected to stem-ringing or treated with high concentration of nitrate. Respiration and N₂ fixation (acetylene reducing activity) were studied in individual nodules along with the concentrations of ATP and magnesium.

There was a high positive correlation between respiration activity and acetylene reduction in soybean nodules. The maintenance respiration in mature nodules corresponded to a CO₂ evolution of 5.5 µmol/g F.W., and the respiratory cost for nitrogen fixation was estimated at 2 mg C liberated/mg N fixed, though this value was probably underestimated due to CO₂ fixation by the nodules. For the nitrogenase activity there was a threshold value of ATP concentration at around 0.15 µmol/g F.W., and the activity increased up to around 0.35 µmol/g F.W., beyond which the ATP concentration did not increase unlike the nitrogenase activity. The values for the magnesium concentration in the nodules detected in the present experiments were above the optimum level.     

调亏灌溉对冬小麦生理机制及水分利用效率的影响

在人工控制试验条件下，采用子母盆栽土培法，以冬小麦为试验材料进行了调亏灌溉试验研究。结果表明，适时适度的水分调亏显著抑制蒸腾速率，而光合速率下降不明显，复水后光合速率又具有超补偿效应，光合产物具有超补偿积累，且有利于向籽粒运转与分配；抑制营养生长，促进生殖生长。冬小麦调亏灌溉的适宜时段为三叶—返青，调亏度为40%～60%田间持水率(θ_F)，历时约55 d；平均比对照增产0.88%～8.25%，节水12.80～18.55%，水分利用效率提高15.96%～32.98%。     

Alleviation of drought stress in winter wheat by late foliar application of zinc,boron, and manganese

In many regions, drought during flowering and grain‐filling inhibits micronutrient acquisition by roots resulting in yield losses and low micronutrient concentrations in cereal grains. A field and a greenhouse experiment were conducted to study the effect of foliar applications of zinc (Zn), boron (B), and manganese (Mn) at late growth stages of winter wheat (Triticum aestivum L.) grown with or without drought stress from booting to maturity. Foliar applications of Zn, B, and Mn did not affect grain yield in the absence of drought. However, under drought, foliar application of Zn and B in the field increased grain yield (15% and 19%, respectively) as well as raising grain Zn and B concentration, while Zn and Mn sprays in the greenhouse increased grain yield (13% and 10%, respectively), and also increased grain Zn and Mn concentrations. Furthermore, under drought stress both in the field and greenhouse experiment the rate of photosynthesis, pollen viability, number of fertile spikes, number of grains per spike, and particularly water‐use efficiency (WUE) were increased by late foliar application of micronutrients. These results indicate that by increasing WUE foliar application of Zn, B, and Mn at booting to anthesis can reduce the harmful effects of drought stress that often occur during the late stages of winter wheat production. These findings therefore are of high relevance for farmers' practice, the extension service, and fertilizer industry.     

灌溉频率对冬小麦产量及叶片水分利用效率的影响

为了探讨中国北方冬小麦高效节水灌溉模式,采用了3种灌溉处理:在拔节期一次灌溉120mm,在拔节期和抽穗期各灌溉60mm及在拔节期、抽穗期和灌浆期各灌溉40mm,研究了在总灌溉量为120mm的情况下,灌溉频率对冬小麦产量及叶片水分利用效率的影响.结果表明,在冬小麦的拔节期和抽穗期各灌溉60mm,显著提高乳熟期和蜡熟期旗叶...     

Selection and characterization of wheat genotypes for saline soils prone to water‐logging

Wheat (Tritcum aestivum L.) genotypes were screened and characterized for performance under salt stress and/or water‐logging. In a solution‐culture study, ten wheat genotypes were tested under control, 200 mM–NaCl salt stress and 4‐week water‐logging (nonaerated solution stagnated with 0.1% agar), alone or in combination. Shoot and root growth of the wheat genotypes was reduced by salinity and salinity × water‐logging, which was associated with increased leaf Na⁺ and Cl^– concentrations as well as decreased leaf K⁺ concentration and K⁺ : Na⁺ ratio. The genotypes differed significantly for their growth and leaf ionic composition. The genotypes Aqaab and MH‐97 were selected as salinity×water‐logging‐resistant and sensitive wheat genotypes, respectively, on the basis of their shoot fresh weights in the salinity × water‐logging treatment relative to control. In a soil experiment, the effect of water‐logging was tested for these two genotypes under nonsaline (EC = 2.6 dS m^–1) and saline (EC = 15 dS m^–1) soil conditions. The water‐logging was imposed for a period of 21 d at various growth stages, i.e., tillering, stem elongation, booting, and grain filling alone or in combinations. The maximum reduction in grain yield was observed after water‐logging at stem‐elongation + grain‐filling stages followed by water‐logging at grain‐filling stage, booting stage, and stem‐elongation stage, respectively. Salinity intensified the effect of water‐logging at all the growth stages. It is concluded that the existing genetic variation in wheat for salinity × water‐logging resistance can be successfully explored using relative shoot fresh weight as a selection criterion in nonaerated 0.1% agar–containing nutrient solution and that irrigation in the field should be scheduled to avoid temporary water‐logging at the sensitive stages of wheat growth.     

The effects of potassium fertilization on water‐use efficiency in crop plants

The supplies of water and nitrogen to a plant during its critical stages of growth are the main factors that define crop yield. A crop experiences irregular water deficits during its life cycle in rain‐fed agriculture. An effective anti‐stress‐oriented approach therefore ought to focus on increasing the units of water productivity. The main objective of this conceptual review is to confirm that adequate K management can be used as an important tool to alleviate the negative effects of water deficit on plant growth, yield‐component formation, and yield. The French and Schultz approach of using the water‐limited yield (WLY) was modified in this review into a graphical form and was used to discriminate between yield fractions that depended on the volume of transpired water from those that were induced by K fertilizer. By using this method, it was possible to demonstrate the extent of several crop (winter wheat, spring triticale, maize, sugar beet) responses to the K supply. Yield increases resulting from K application mostly appeared under conditions of mild water deficit. As described for sugar beet, finding the critical period of crop K sensitivity is a decisive step in understanding its impact on water‐use efficiency. It has been shown that an insufficient supply of K during crucial stages in the yield formation of cereals (wheat, spring triticale), maize, and sugar beet coincides with a depressed development in the yield components. The application of K fertilizer to plants is a simple agronomic practice used to increase crop tolerance to a temporary water shortage. It may be that the improvement of a plant's access to K during mild water‐deficiency stress will increase water uptake by the root cells, which in turn increases their osmotic potential and thereby allows extension growth. This growth in turn promotes access to other mineral elements (including nitrogen) and water, which favor plant growth and yield.     

虚实并存耕层提高春玉米产量和水分利用效率

为了探明耕层构造对春玉米产量及水分利用效率的影响,在农业部阜新农业环境与耕地保育科学观测实验站利用长期定位试验,设置了虚实并存耕层(furrow loose and ridge compaction plough layer,FLRC)、全虚耕层(all loose plough layer,AL)、全实耕层(all compaction plough layer,AC)、以及作为对照(controlled trial,CK)的上虚下实耕层(up loose and down compaction plough layer,ULDC)4种耕层结构,研究了不同耕层构造对春玉米产量及水分利用效率的影响。利用2011和2012年数据分析结果表明,不同耕层构造对春玉米产量影响显著(P0.05),2a平均表现为FLRCALULDCAC,FLRC和AL比CK分别增加16.39%、5.30%,收获指数在0.38~0.44之间。在平水年(2011)和丰水年(2012)虚实并存耕层和全虚耕层均可有效蓄积降水,改善土壤水分状况,明显提高玉米的降水利用效率,2011年FLRC比ULDC提高11.95%(P0.05);2012年FLRC和AL分别比CK提高21.23%(P0.05)和12.43%(P0.05);不同降雨年型和不同耕层结构对作物水分利用效率(water use efficiency,WUE)影响不同,2011年FLRC比CK增加15.68%(P0.05),2012年FLRC比CK增加23.13%(P0.05),2a平均提高18.43%。综合分析认为,虚实并存耕层是提高土地生产力和农田水分利用效率的最优耕层结构。该研究为辽西旱作农业区合理耕层构建、确定适宜的耕作技术和实现作物的高产稳产提供参考。     

不同钾硼水平下棉花生长及钾硼利用效率的差异

用鄂抗8号棉花为试验材料,以水培的方法研究了不同钾、硼水平下棉花的生长状况及钾、硼的利用效率。结果表明:与正常处理(K 20 mg/L,B 0.2 mg/L)棉花相比,(1)缺钾(K 2 mg/L,B 0.2 mg/L)阻碍棉花地上部正常生长、干物质的积累,叶绿素合成受阻,但促进了根的伸长,缺钾不利于棉株对硼的吸收和利用,增加钾供应量可以促进硼的吸收利用。(2)缺硼(K 20 mg/L,B 0.002 mg/L)不利于棉株生长,棉株干物质积累量减少,不利于棉花对钾的吸收利用。(3)缺钾缺硼(K 2 mg/L,B 0.002 mg/L)时,棉花的生物量、SPAD值和钾、硼积累量均显著降低,钾的利用效率升高了143%,但对硼的利用受到抑制。研究结果表明,缺钾阻碍棉花对硼的吸收利用,缺硼不利于棉花对钾的吸收利用,而缺钾缺硼时,棉花对钾的利用受到促进,对硼的利用受到抑制。     

春小麦留茬处理对复种油菜产量和水分利用效率的影响

为了减少麦茬焚烧、控制麦茬焚烧污染及提高留茬的利用效率,2009年7－10月在石羊河绿洲灌区进行不同留茬处理（焚烧、翻耕和立茬免耕）对麦茬复种油菜的研究。结果表明,与休闲地相比,立茬免耕复种油菜可获得利润 3?275元/hm2;焚烧、翻耕（传统耕作）和立茬免耕处理的油菜籽粒产量分别为1?549、1?331和1?222 kg/hm2,水分利用效率分别为5.73、3.81和5.71 kg/hm2/mm,经济效益分别为4?485、2?929和3?275元/hm2;仅从作物籽粒产量、水分利用效率和经济效益等方面考虑,秸秆焚烧处理达到最大值, 这就是焚烧屡禁不止的原因。尽管传统耕作的油菜籽粒产量高于立茬免耕,但传统耕作的水分利用效率和经济效益显著低于立茬免耕。立茬免耕具有环保、相对较高水分利用效率和经济效益等效果,尤其有利于环境保护和旱地农作,值得大面积推广。结合大田推广示范研究成果,提出适宜于石羊河绿洲灌区的留茬免耕机械直播复种油菜技术。     

Timely supplemental irrigation changed nitrogen use of wheat by regulating root vertical distribution

Crop nitrogen (N) uptake depends on the root absorption area and the soil N availability which are closely related to the soil water status. With the increasing water shortages in the North China Plain, supplemental irrigation (SI) to winter wheat is a promising technique. To clarify the relationships between water and nitrogen use, four SI regimes in Tritcum aestivum L. cv. Jimai 22 were set up: no‐irrigation after emergence (T1), SI at jointing and anthesis (T2), SI at sowing, jointing and anthesis (T3), and SI at pre‐wintering, jointing and anthesis (T4). The results indicate that T2 had higher root length density (RLD) and root surface area density (RAD) in the 0–20, 60–80, and 80–100 cm soil layers, as well as higher post‐anthesis N uptake from soil by 23–26% in 2012–2013 and 162–177% in 2013–2014, compared to T3 and T4. The grain yield under T2 was lower than T3 but was not significantly different from T4, whereas its water use efficiency (WUE) was higher relative to both T3 and T4. There were no significant differences among T2, T3, and T4 in N use efficiency (NUE). The N uptake after jointing and WUE were positively correlated with the RLD and RAD in the 0–20 cm soil layer. The NUE was positively correlated with the RLD and RAD in the 20–40 cm soil layer. These results indicate that timely SI at jointing and anthesis was dependent on a suitable water supply at sowing, which increased the soil water content in the upper soil layer after jointing and improved the absorption area of the roots in both the deep and surface soil layers; this further improved the post‐anthesis N uptake from the soil and the WUE. This approach can be a valuable way to maintain high grain yields and NUE in winter wheat while using less irrigation and achieving higher WUE in the North China Plain.     

灌溉对冬小麦水分利用效率的影响研究

通过设计不同的灌溉处理，从叶片水平、群体水平和产量水平3个层次系统分析了冬小麦水分利用效率(Water Use Efficiency, WUE)的变化特点及其内在联系。结果表明：叶片水平WUE或蒸腾效率(Transpiration Efficiency, TE)是群体蒸散效率基础；气孔运动机制及光合作用和蒸腾作用对环境变化响应的差异是叶片水平WUE的生理基础；而产量水平WUE是群体蒸散效率与收获指数共同决定的。随耗水量的增加，叶片光合速率、群体干物质积累及籽粒产量都呈二次曲线增长趋势，结果使叶片水平WUE     

调亏灌溉对苜蓿水分利用效率和品质的影响

从高产、优质和高效的三重目标出发，在甘肃秦王川灌区通过大田试验研究了调亏灌溉对苜蓿水分利用效率和品质的影响。结果表明：轻度水分亏缺下(土壤含水率为60%～65%田间持水量)苜蓿产量较充分灌溉(土壤含水率为65%～70%田间持水量)没有显著差异，而苜蓿的水分利用效率、粗蛋白含量与其余各处理间存在显著差异，其值均达到了最大，分别达2.10 kg/m³和13406.7 ug/g。     

在施钾条件下灌溉水稻的养分吸收和利用效率研究

Potassium is one of the most important nutrients for rice production in many areas of Asia, especially in southeast China where potassium deficiency in soil is a widespread problem. Field experiments were conducted for four consecutive years in Jinhua City, Zhejiang Province, to determine utilization of nutrients (N, P and K) by inbred and hybrid rice and rice grain yields as affected by application of potassium fertilizer under irrigated conditions. Grain yield and nutrient harvest index showed a significant response to the NPK treatment as compared to the NP treatment. This suggested that potassium improved transfer of nitrogen and phosphorus from stems and leaves to panicles in rice plants. N and P use efficiencies of rice were not strongly responsive to potassium, but K use efficiency decreased significantly despite the fact that the amount of total K uptake increased. A significant difference between varieties was also observed with respect to nutrient uptake and use efficiency. Hybrid rice exhibited physiological advantage in N and P uptake and use efficiency over inbred rice. Analysis of annual dynamic change of exchangeable K and non-exchangeable K in the test soil indicated that non-exchangeable K was an important K source for rice. Potassium application caused an annual decrease in the concentration of available K in the soil tested, whereas an increase was observed in non-exchangeable K. It could be concluded that K fertilizer application at the rate of 100 kg ha^-1 per season was not high enough to match K output, and efficient K management for rice must be based on the K input/output balance.     

伤根对春小麦光合特性及水分利用效率的影响研究

盆栽春小麦伤根处理试验结果表明 ,苗期春小麦伤根适度处理可提高叶片光合速率及水分利用效率 ,促进光合产物积累 ,增加春小麦产量。拔节期春小麦伤根处理则抑制春小麦生长 ,降低其产量。     

湖北省早、中、晚稻施钾增产效应及钾肥利用率研究

2006～2009年,在湖北省18个县（市、区）布置多点田间肥效试验,研究在当前生产条件下推荐施用钾肥对早、中、晚稻产量及其构成因素的影响,分析当前水稻生产中的钾肥吸收和利用状况。结果表明,在氮、磷肥的基础上,早、中、晚稻施用钾肥的增产量平均分别为716、679和691 kg/hm2,增产率平均分别为12.6%、9.6%和12.0%,钾肥对产量的贡献率平均分别为10.8%、8.2%和10.3%。说明当前生产条件下,高产水稻生产必须施用钾肥。施钾之所以增产,早稻主要由于单位面积有效穗数增加,中稻主要由于单位面积有效穗数和每穗粒数增加,而晚稻主要由于每穗粒数增加和结实率提高所致。施用钾肥促进了水稻总吸钾量及百千克子粒吸钾量的提高和钾素收获指数的下降。在当前生产条件和推荐施钾量水平下,早、中、晚稻百千克子粒吸钾（K2O）量平均分别为2.96、3.45和2.72 kg,钾肥（K2O）农学利用率分别为9.6、8.2和7.2 kg/kg,偏生产力分别为92.3、101.5和75.4 kg/kg,吸收利用率分别为47.1%、53.8%和46.3%,生理利用率分别为21.1、24.1和23.7 kg/kg,土壤钾素依存率分别为78.0%、83.0%和70.4%。3种类型水稻对钾素的吸收和利用虽有不同,但其吸收的钾都主要来自于土壤,因此改善土壤供钾能力是提高水稻产量和节约钾肥资源的有效措施。     

控制灌溉水稻叶片水平的水分利用效率试验研究

根据现场试验资料,分析了晚稻叶片水平的水分利用效率的日变化与全生育期变化,叶片的水分利用效率与气孔导度及外界影响因子包括光合有效辐射、土壤水分、叶气温差等的相互关系。结果表明：控制灌溉水稻叶片的水分利用效率在较高土壤水分时与对照处理差别不明显,适度土壤水分调控可以获得较高的水分利用效率;全生育期水稻叶片的水分利用效率随土壤水分变化而波动,过高过低的土壤水分均不利于水分利用效率的提高;叶片的光合速率、蒸腾速率与水分利用效率均随气孔导度的增加表现出先增后减的变化规律。水稻叶片的水分利用效率影响因素分析显示：水分利用效率随叶气温差、二氧化碳浓度和空气湿度的增加而增加;有利于获得较高水分利用效率的气孔导度、光合有效辐射、空气温度和土壤水分范围分别是200～350 μmol·m^-2·s^-1、400～900 μmol·m^-2·s^-1、28～34℃和85%～90%的土壤饱和含水率。     

Nitrogen metabolism is related to improved water‐use efficiency of nodulated alfalfa grown with sewage sludge under drought

Leguminous plants grown in sewage sludge–amended soils can acquire nitrogen by assimilation of nitrate and ammonium from the soil solution or from atmospheric‐dinitrogen (N₂) fixation through association with N₂‐fixing bacteria. We proposed that operation of both metabolic processes could contribute to alleviate the impact of drought in sludge‐treated plants. A greenhouse experiment was conducted to evaluate the involvement of nodule metabolism in the use efficiency of water and N in sludge‐treated plants. Treatments comprised (1) plants inoculated with rhizobia and amended with sewage sludge; (2) plants inoculated with rhizobia without any amendment; and (3) noninoculated plants supplied with ammonium nitrate, each under well‐watered and drought conditions. Under drought, sludge‐treated plants had increased plant growth and higher photosynthetic and water‐use efficiencies than untreated plants. Drought stimulated nitrate reductase and GS/GOGAT activities but did not affect the activities of phosphoenolpyruvate carboxylase and malate dehydrogenase or the leghemoglobin concentration. The results suggest that under drought conditions, both N₂ fixation and nitrate assimilation in nodules of sludge‐treated plants contributed to improve plant N supply and to increase the drought tolerance of alfalfa.